Use cert-manager to generate certs for tests (apache#306)

* Use cert-manager to generate certs for tests

* Install Cert-Manager in test env

### Motivation

Currently, we use hard coded certificates for the tests. Instead, we can use Cert Manager to generate the certificates. The primary benefit of this change is that it ensure we're testing the cert manager integration.

### Modifications

* Remove `.ci/tls` directory since we no longer need these certs.
* Remove `scripts/pulsar/clean_tls.sh` (it wasn't used)
* Remove `scripts/pulsar/upload_tls.sh` since we are not uploading any certs
* Update the `helm.sh` test script
* Update the `.ci/clusters` configurations to generate the relevant cert manager manifests

### Verifying this change

- [ ] Make sure that the change passes the CI checks.

.ci/clusters/values-bk-tls.yaml

@@ -67,7 +67,8 @@ tls:
   bookie:
     enabled: true
 
-# disable cert manager
+# enable cert-manager
 certs:
   internal_issuer:
-    enabled: false
+    enabled: true
+    type: selfsigning

.ci/clusters/values-broker-tls.yaml

@@ -69,7 +69,8 @@ tls:
   broker:
     enabled: true
 
-# disable cert-manager
+# enable cert-manager
 certs:
   internal_issuer:
-    enabled: false
+    enabled: true
+    type: selfsigning

.ci/clusters/values-tls.yaml

@@ -73,7 +73,8 @@ tls:
   zookeeper:
     enabled: true
 
-# disable cert-manager
+# enable cert-manager
 certs:
   internal_issuer:
-    enabled: false
+    enabled: true
+    type: selfsigning

.ci/clusters/values-zk-tls.yaml

@@ -67,7 +67,8 @@ tls:
   zookeeper:
     enabled: true
 
-# disable cert manager
+# enable cert-manager
 certs:
   internal_issuer:
-    enabled: false
+    enabled: true
+    type: selfsigning

.ci/clusters/values-zkbk-tls.yaml

@@ -69,7 +69,8 @@ tls:
   bookie:
     enabled: true
 
-# disable cert manager
+# enable cert-manager
 certs:
   internal_issuer:
-    enabled: false
+    enabled: true
+    type: selfsigning

.ci/helm.sh

@@ -105,9 +105,9 @@ function ci::install_pulsar_chart() {
 
     echo "Installing the pulsar chart"
     ${KUBECTL} create namespace ${NAMESPACE}
+    ci::install_cert_manager
     echo ${CHARTS_HOME}/scripts/pulsar/prepare_helm_release.sh -k ${CLUSTER} -n ${NAMESPACE} ${extra_opts}
     ${CHARTS_HOME}/scripts/pulsar/prepare_helm_release.sh -k ${CLUSTER} -n ${NAMESPACE} ${extra_opts}
-    ${CHARTS_HOME}/scripts/pulsar/upload_tls.sh -k ${CLUSTER} -n ${NAMESPACE} -d ${PULSAR_HOME}/.ci/tls
     sleep 10
 
     echo ${HELM} install --set initialize=true --values ${value_file} ${CLUSTER} ${CHARTS_HOME}/charts/pulsar